提出建议：You should... — 英语词汇题
题目
补全句子（每空一词，首字母已给出），使每句成为一条安全建议。
1. You s________ cross the street when the light is green.
2. You should be c________ near the river.（小心）
3. You s________ not play football in the street.
4. You should l________ to the teacher in class.